The present invention relates to a novel grid material that is capable of being joined with a plastic molding to provide a shielding structure for shielding electromagnetic waves from an electronic device. Specifically, the grid material is a nickel-coated mesh-like material or substrate that is annealed and calendared together to provide a bonded unitary grid structure. The grid material provides a conductor in the shielded structure and provides a flexible grid material which readily permits the insertion and placement with respect to an electrical mold cavity to permit the insert molding of the shielding housing.
Electromagnetic interference (E.M.I.) shielding structures exist to provide protection for an electronic instrument or device from electromagnetic energy, including radio frequency interference (R.F.I.). The shielding structures hopefully provide protection for the electronic device by preventing electromagnetic wave energy from penetrating the device, as well as escaping from the device. However, electromagnetic shielding products have generally been made by the formation of sheet metal boxes; conductive paints applied to a plastic housing, die cast parts to construct a housing and filled resins containing metal fibers. However, such prior art sheet metal devices for providing shielding structures have found only limited application because of the difficulties of weight restrictions in shielding housings, the inability to make round shapes, noise problems and the requirement of multiple parts. Conductive paints include electroplating metal onto a plastic, a technique which requires a second processing step, provides poor performance, is cost prohibitive, presents environmental problems and is susceptible to chipping and flaking. Filled resins are very expensive and destroy insert molding tooling and exhibit poor shielding properties. For example, in utilizing a die cast or plate material, the resultant shielding housing used to enclose and shield an electronic device requires external connections and supplemental shielding at the joints or corners of the enclosure to provide the box-like enclosure. Such assembly techniques are expensive and time consuming and oftentimes result in a structure which does not properly shield the enclosed device. Accordingly, such shielding structures and approaches have found only limited acceptance. Finally, such shielding structures may require is complex conductive junctions and connections between shielding panels, assembly techniques that are expensive and time consuming and which oftentimes result in unacceptable shielding housings.